1. Field of the Invention
The present invention relates to freshness preserving agent for e.g. flowers, vegetables and fruits.
2. Discussion of Background
Heretofore, ethylene has been known as a modified gas component generated from vegetables and fruits. The amount of ethylene generated from plant bodies is extremely large, and in the case of climacteric fruits, the amount is said to reach 10 ml/kg/day. On the other hand, the threshold value of ethylene which induces a physiological change is extremely small at a level of from 0.1 to 3 ppm.
As a freshness preserving agent which removes such ethylene as the modified gas component, active carbon, potassium permanganate, bromine-absorbed carbon or active carbon having palladium chloride supported thereon, has been, for instance, known.
However, with active carbon, the ethylene absorptivity at a low ethylene concentration is low, and the effect as a freshness preserving agent is still inadequate. Potassium permanganate contains heavy metals, and its use for food products is very dangerous and improper because of the toxicity and the explosive nature. Bromine-absorbed carbon (U.S. Pat. No. 4,256,773) is not suitable for food products, since bromine and ethylene react to each other to form ethylene dibromide which has a carcinogenic nature. In the case of active carbon having palladium chloride supported thereon (Japanese Examined Patent Publication No. 25340/1986), there is no problem of toxicity, but the speed for the removal of ethylene is slow, and the amount of ethylene thereby treated is small, and the effect is inadequate in that it is impossible to completely remove ethylene to a low concentration.